This project is involved in an analysis of the characteristics of the single sucrose gap voltage clamp technique, as applied to cardiac muscle, and the application of that analysis to the understanding and interpretation of data resulting from that technique. Simultaneously, cardiac excitation- contraction coupling is being studied by comparing the electrical and mechanical effects exerted by a series of inotropic agents: Ca, isoproterenol, caffeine, and a Ca blocker. Specific studies in cardiac electrophysiology currently involve the analysis of outward current carrying ions, and alterations of these and inward Ca movement as a result of inotropic interventions. The various results are continually incorporated into a numeric model of the muscle which includes both the electrical characteristics of the membrane, and the spatial effects of preparation geometry as used in a single sucrose gap.